ino_to_fsbo
#define ino_to_fsbo(fs, x) (((x) - 1) % (fs)->mfs_inodes_per_block)
#define ino_to_fsbo(fs, x) (((x) - 1) % (fs)->e2fs_ipb)
#define ino_to_fsbo(fs, x) (((ino_t)(x)) % FFS_INOPB(fs))